This invention relates generally to a system and device for conveying. More specifically, the invention relates to a unit handling roller conveyor system driven by an external direct current (“DC”) motor.
Unit handling roller conveyor systems generally comprise sections, or zones, made up of conveyor frames supporting individual rollers. The rollers of each zone are driven by a motor, and transport items from one end of the zone to the other. Each zone may have separate controls, and the zones and associated controls are connected with other zones to form a larger conveying system. In recent years, several advancements have been made to roller conveyor systems. For example, the development of low voltage DC motorized drive rollers (MDRs) have resulted in reduced power consumption, decreased noise and fewer maintenance requirements. Another advancement involves the use of elastomeric o-ring type belts that are used with the MDRs, function to drive the idler rollers in each zone in response to rotation of an MDR.
Despite these advancements, motorized rollers are not without some limitations and drawbacks. A typical commercially available motorized roller has support bearings, a motor, a gear reducer and an internal drive mechanism axially stacked within a casing. Because of this stacking, the minimum overall length of commercially available motorized rollers is in the range of 11″, thereby preventing use of motorized rollers in very narrow conveyors. Further, the minimum diameter of commercially viable motorized rollers is approximately 1.9″which precludes the use of motorized rollers in conveyor designs for small packages. Furthermore, reliability is an ongoing issue because motorized rollers are only rated for about two years of continuous use due to gear failure.
Therefore, there is a need for an externally mounted, compact, direct drive, low voltage and reliable DC motor to drive the rollers of a conveyor system. There is also a need for the drive motor to fit within the footprint of the section of roller conveyor. There is further a need for a roller conveyor system having significant reductions in power consumption, noise generation and maintenance requirements, as well as a need for a roller conveyor system that permits shorter, smaller diameter rollers, higher efficiency, and more robust lead assemblies.